Independent and Combined Effect of Some Soil Tillage Systems on Nitrogen and Carbon Concentration in Soil Structural Units of Haplic Chernozems

作     者：Margarita Nankova Peter Yankov 

作者机构：Dobrudzha Agricultural Institute General Toshevo 9520 Bulgaria Technical University of Varna Varna 9010 Bulgaria 

出 版 物：《Journal of Agricultural Science and Technology(B)》 (农业科学与技术（B）)

年 卷 期：2015年第5卷第7期

页      面：465-476页

学科分类：090101[农学-作物栽培学与耕作学] 09[农学] 0901[农学-作物学] 

主　　题：Soil tillage systems soil C total soil N soil structural units. 

摘      要：This paper aimed at studying the effect of different types of soil tillage systems on the change of total carbon （C） and nitrogen （N） in the soil structural units of different size after dry structural analysis of soil. The research was carried out in a 6-field rotation system （grain maize-wheat-sunflower-wheat-bean-wheat） at the end of the 2nd rotation. Six out of 24 soil tillage systems were selected; they were applied independently and in combination in the crop rotation. After that, they were compared to the system with constant deep plowing. So a total of seven soil tillage systems were investigated. The selected systems for main soil tillage were the following： plowing （control variant）, disking, cutting, nil tillage （direct sowing）, plowing-disking, plowing-nil tillage, disking-nil tillage. Three depths of 0-10, 10-20 and 20-30 cm were studied, as well as soil structural units were of the following sizes： 〉 10 mm, 10-5, 5-3, 3-1, 1-0.25 mm and 〈 0.25 mm. As a result of systematic implementation of different soil tillage systems, higher N and C concentrations were established by the layers according to constant plowing. Constant disking and its alternation with nil tillage increased the total N concentration with 15.6% and 11.1%, respectively, in comparison with the constant plowing. The same was valid for C concentration in soil, but the highest increase was established in the variants with constant cutting and nil tillage. The exceeding was with 14.0% and 13.2%, in comparison to constant plowing. The redistribution of N and C depending on the structural soil units was most expressed in the 0-10 cm and 10-20 cm layers. The highest amounts of C and N were found in the soil units with size less than 5 mm, mainly in the 〈 0.25 mm fraction. At depth of 20-30 cm, the role of the size of soil structural units for C and N redistribution decreased strongly. The values of C/N ratio were moderate only under the use of constant disking. This index was low under all othe